import {
  HISTORY_MAX_ITEMS,
  HISTORY_STORAGE_KEY,
  type CalcHistoryEntry,
} from "@/lib/history/types";

export function loadHistory(): CalcHistoryEntry[] {
  if (typeof window === "undefined") {
    return [];
  }
  try {
    const raw = localStorage.getItem(HISTORY_STORAGE_KEY);
    if (!raw) {
      return [];
    }
    const parsed = JSON.parse(raw) as CalcHistoryEntry[];
    return Array.isArray(parsed) ? parsed : [];
  } catch {
    return [];
  }
}

export function saveHistoryEntry(
  entry: Omit<CalcHistoryEntry, "id" | "createdAt">,
): CalcHistoryEntry {
  const full: CalcHistoryEntry = {
    ...entry,
    id: crypto.randomUUID(),
    createdAt: new Date().toISOString(),
  };
  const list = [full, ...loadHistory()].slice(0, HISTORY_MAX_ITEMS);
  localStorage.setItem(HISTORY_STORAGE_KEY, JSON.stringify(list));
  return full;
}

export function deleteHistoryEntry(id: string): void {
  const list = loadHistory().filter((e) => e.id !== id);
  localStorage.setItem(HISTORY_STORAGE_KEY, JSON.stringify(list));
}

export function downloadMarkdown(content: string, filename: string) {
  const blob = new Blob([content], { type: "text/markdown;charset=utf-8" });
  const url = URL.createObjectURL(blob);
  const a = document.createElement("a");
  a.href = url;
  a.download = filename.endsWith(".md") ? filename : `${filename}.md`;
  a.click();
  URL.revokeObjectURL(url);
}

export function buildHistoryMarkdown(entry: CalcHistoryEntry): string {
  const lines = [
    `# ${entry.title}`,
    "",
    `- 类型：${entry.mode}`,
    `- 时间：${new Date(entry.createdAt).toLocaleString("zh-CN")}`,
    `- 问事：${entry.question}`,
    "",
    ...Object.entries(entry.meta).map(([k, v]) => `- ${k}：${v}`),
    "",
    "---",
    "",
    entry.completion,
  ];
  return lines.join("\n");
}